(1) Field of the Invention
The present invention relates to a method for transmitting and receiving an order wire, used in the maintenance of transmission paths such as SONET, SDH and the like as well as relay devices, between exchanges of ATM networks.
(2) Prior Art
Recently, in order to realize broadband services in the B-ISDN (Broadband Integrated Service Digital Network), simultaneous networks by means of multiplex transmission such as SONET (Synchronous Optical Network) which is the standard method of the North American system, SDH (Synchronous Digital Hierarchy) which has been adopted as the international standard centering on Europe, and the like, have been proposed.
This type of simultaneous network transmits and receives data of a frame structure, formed by a payload section made by multiplexing a number of communication data items whose transmission speeds differ, and an overhead section which is added to the head of the payload data and stores control information for maintaining and managing networks.
The format of the overhead in SDH is shown in FIG. 11.
The overhead of SDH comprises a relay section overhead and a multiplex section overhead.
The relay section overhead is a region for storing control information relating to the maintenance and management of a transmission path connecting relay device to relay device, and has a 9-byte data region of a triple-layered frame structure.
The multiplex section overhead is a region for storing control information relating to the maintenance and management of the relay device and the transmission path for connecting between one end-station relay device and another end-station relay device, and has a 9-byte data region of a five-layered frame structure.
Further, between the relay section overhead and the multiplex section overhead, a 1 (byte).times.1 (layer) pointer is included. This pointer is a pointer for indicating the position of a path overhead which stores information concerning the paths of each item of the multiplexed data.
Also, an order wire region for storing audio data is provided in the multiplex section overhead. Further, there is also a region known as BIP-8 for storing audio data in the relay section overhead.
According to this type of the method, a network maintenance worker can map, in frame structure overheads, information relating to faults in and restoration of transmission paths, information relating to faults in and restoration of relay devices, and information relating to faults in and restoration of end-station relay devices. Accordingly, the above method has the advantage of being able to effectively perform detection of fault information in a communication process and detection of restoration information.